UART2 Status: Partly disabled conflict with PA mapped with GPIO_Output

[Moza]

Hi, a noob post from a noob developer. I am trying to understand how STM32Cube ide works. I guess by default UART2 has set as UART_TX - PA2, UART_RX - PA3. I have reconfigured PA1 and PA2 as GPIO_OutPut and set UART_TX - PA14 and UART_RX - PA15. There is a yellow warning sign beside UART2 that says, 'UART2 Partly disa bled conflict with PA mapped with GPIO_Output'

Below is the new configuration:

And below is the old configuration: 



In that case, can I continue to use the new configuration? 

Also planning to reconfigure the below pins: Will this be any problem? Do I have to configure RCC_OSC32_IN, RCC_OS32_OUT, RCC_OSC_IN, and RCC_OSCOUT? What do these use for?

Thank you in advance. 

[STTwo-32]

Hello @Moza 

For the warning, means that you can't enable only the hardware flow control since it need to use the PA1 pin for an alternate function and not as GPIO Output. So if you want to use it you have to set PA1 as USART2_RTS. For the other Pins you mentionned on the third screenshot, they are used to connect external Clock source ( LSE and HSE). If you are not going to use them, you can disable them or configure them as gpio (for more details refer to the decreption inder table 13 of the https://www.st.com/resource/en/datasheet/stm32f091rc.pdf)

Best Regards.

STTwo-32 

[Moza]

Hi, Thanks for your reply. So, does that mean I can not use PA1 as GPIO_Output?

[STTwo-32]

If you are looking to use the USART2 in a configuration that does not need PA1 (Asynchronous mode for example), you can use PA1 AS GPIO Output. But if you are going to use one of the modes that show a warning message that it will need PA1 to work, then you can't use PA1 as GPIO OUTPUT.

Best Regards.

STTwo-32 

[Moza]

Hi again, only Asynchronous mode shows this warning. Can you tell me or share a reference link for all the mode details so that I can understand which mode I need? I am using STM32 NUCLEO-F091RC UART2 MCU. 

[STTwo-32]

For the Asynchronous mode, you can use the PA1 as GPIO Output but if you are looking to enable the RS232 (just bellow the mode) you can't since you will need the PA1 (As you can see on the warning).

Best Regards.

STTwo-32 

[Moza]

I want to activate RS458 on controller startup so that I can use it with the Nvidia Jetson Orin Nano Devkit. 

The debug UART of the NVIDIA Jetson Orin Nano (UART2) is routed to the RS485 transmitter on the connector board. This transmitter is disabled by default (circuit design), so it is neccessary to activate the transmitter before the NVIDIA Jetson boots to make sure that there is no loss of data/information during boot process of the NVIDIA Jetson.
To activate the RS485 transmitter, the I2C-PortExpander on the connector board must be configured accordingly.

[STTwo-32 · Accepted solution]

If you are looking to activate the Hardware Flow Control (RS485), you have to set the PA1 to USART2 _DE. So, you can't use it as GPIO Output.

Best Regards.

STTwo-32